The present invention relates to centrifugal clutches, and particularly, to noise-attenuation systems for quieting running noises produced during operation of centrifugal clutches. More particularly, the present invention relates to centrifugal clutches outfitted with sound-deadening pads.
Clutches are used in a variety of mechanical systems to transmit torque from a motor to a driven part (e.g., drive belt or chain) of a mechanism. A clutch is a coupling used to connect and disconnect a driving and a driven part of a mechanism. A wide variety of clutches are known. A positive contact clutch transmits power from a driving shaft to a driven shaft by means of jaws or teeth. A disc clutch is able to transmit torque from an input shaft to an output shaft because of the frictional force developed between two plates or discs. A cone clutch is another type of axial friction clutch in which a cone fits in a cup. Electric clutches, hydraulic or pneumatic clutches, and overrunning clutches are also used to produce torque transmission.
A centrifugal clutch is designed to "engage" and transmit torque from an input shaft to an output shaft whenever some minimum rotational speed has been exceeded. It has been observed that conventional centrifugal clutches produce a lot of clicking and clattering sounds during operation due to engagement of the rotating clutch components. In some environments, excessive noise can be a problem. For example, consumers are unhappy if the clutch included in an appliance used in the home is noisy during operation. Although some electric clutches operate quietly, they are expensive and include a lot of components.
What is needed is a quiet-running centrifugal clutch that is operable to transmit power from an input shaft to an output shaft quietly and effectively. Such a centrifugal clutch would provide a suitable replacement for expensive solenoid-actuated clutches in the home appliance industry and would represent a substantial improvement over noisy conventional centrifugal clutches.
In accordance with the present invention, a centrifugal clutch includes a pair of clutch shoes, a rotor, and means for holding the clutch shoes and the rotor in engaged relation so that rotation of the rotor at a speed in excess of a minimum speed imparts enough centrifugal force to the clutch shoes to move the clutch shoes to grip and rotate the holding means, thereby producing torque transmission.
Each clutch shoe is formed to include at least one clutch shoe pocket. A resilient buffer member is mounted in each clutch shoe pocket. The rotor includes at least one rotor arm extending into one of the clutch shoe pockets to impart centrifugal force to the clutch shoe during rotation of the rotor. Each rotor arm is arranged so that it always engages its companion resilient buffer member during rotation of the rotor to deaden sound produced by movement of the rotor arm in its clutch shoe pocket.
In preferred embodiments, the holding means is a clutch drum and each clutch shoe includes three pockets arranged in the clutch drum to position the three clutch shoe pockets adjacent to the rotor. Illustratively, the rotor includes a rotor hub and six rotor arms projecting outwardly from the rotor hubs like spokes on a wheel. Three of the rotor arms extend into the three pockets formed in one of the clutch shoes and the other three rotor arms extend into the three pockets formed in the other clutch shoe. It will be understood the number of rotor arms and clutch shoe pockets may vary from one application to another.
Illustratively, a motor-driven power input shaft is attached to the rotor and a power output shaft is attached to the clutch drum. In operation, the motor-driven power input shaft rotates the rotor causing the rotor arms to rotate the clutch shoes. Once the rotor is turning at a fast enough speed, the rotor arms impart enough centrifugal force to the clutch shoes to move the shoes outwardly to grip the clutch drum. This gripping action causes the drum to rotate with the rotor, thereby causing the power output shaft to rotate with the power input shaft and produce torque transmission.
Illustratively, each resilient buffer member is a thin-walled liner made of plastics molding material. Each resilient buffer member functions to cushion the impact between the clutch shoe and one of the rotor arms to produce a quiet-running centrifugal clutch. Preferably, each resilient buffer member is a "snap-in liner" that is retained in its clutch shoe pocket under a compression load by tight-fitting engagement with the clutch shoe. Alternatively, one or more of the resilient buffer members could be a "snap-on liner" or a "slide-on liner" of the rotor arms.
Resilient buffer members in accordance with the present invention function to attenuate noise caused by operation of the centrifugal clutch at low cost. Advantageously, a low-cost centrifugal clutch outfitted with resilient buffer pads can be used in lieu of a more complex and expensive electric solenoid-actuated clutch of the type commonly used in the home appliance industry.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.